feat(data/polynomial/laurent): laurent polynomials are a module over polynomials (#14121)
feat(data/polynomial/laurent): laurent polynomials are a module over polynomials (#14121)

This PR only introduces the instance `module R[X] R[T;T⁻¹]`.

I isolated it from the rest, since I want to give special attention to whether there might be any issues declaring it a global instance and whether it should be localized or even simply a def.  Edit: Eric seems happy with this instance!





leanprover-community/mathlib,leanprover-community/mathlib